In-service nuclear power station main equipment safety end weld defect repairing method

Abstract

The invention discloses an in-service nuclear power station main equipment safety end weld defect repairing method. The method comprises the following steps that 1, multi-weld-pass multi-layer weldingis applied to the low-alloy steel side of a stainless steel main pipeline and a low alloy steel main device which are in welded connection from exterior to interior; 2, water is led into the stainless steel main pipeline, and multi-layer bead welding is applied to all positions; 3, whole bead welding of follow-up weld passes is performed on the bead welded priming layer from low-alloy steel sideto the stainless steel side. Compared with the prior art, the in-service nuclear power station main equipment safety end weld defect repairing method has the advantages that multiple layers of stresscorrosion resisting materials are welded to the outer wall of a pipeline with defects on the inner wall, so that the strength of the pipeline with the defects is improved; meanwhile, compression stress is generated on the inner wall of the pipeline, so that the defects are prevented from being further expanded, the repairing method is simple and rapid, the whole pipeline with overproof defects atthe safety end welding bead does not need to be replaced, and the safety operation of a nuclear power station can be ensured.

Description

Technical field [0001] The present invention belongs to the technical field of nuclear power. More specifically, the present invention relates to a method for repairing weld defects at the safety end of main equipment of an in-service nuclear power plant. Background technique [0002] The main equipment in the in-service nuclear power plant includes: pressure vessel, steam generator and voltage stabilizer, which are respectively connected to the main pipeline through a safe end. The safety end of the main equipment has a complex structure, including multiple welding forms and multiple material types. The weld forms include isolation layer welds, surfacing welds and dissimilar steel butt welds, and materials include alloy steel, nickel-based alloys and stainless steel Therefore, the manufacturing process is complicated, the welding difficulty is very high, the welding of dissimilar metals is prone to welding defects, and the welding residual stress is also high. The main equipmen...

AI Technical Summary

Problems solved by technology

The structure of the safety end of the main equipment is complex, including various welding forms and various types of materials. The weld forms include isolation layer welds, surfacing welds and dissimilar steel butt welds, and the materials include alloy steel, nickel-based alloys and stainless steel. etc., so the manufacturing process is complicated, the welding difficulty is very high, the welding of dissimilar metals is prone to welding defects, and the welding residual stress is also high

The main equipment is subjected to high temperature, high pressure, neutron radiation and high and low temperature fatigue loads during operation. Therefore, the safety end is prone to stress corrosion and cracks, which seriously affects the safe operation of the equipment.

[0003] At present, boron crystals have been found at the safety end of main equipment in many nuclear power units in foreign countries. It takes a lot of money to deal with the safety end defects, and the maintenance cycle is also very long (> 6 months). The direct economic loss caused by the shutdown of the nuclear power plant huge

[0004] Although the main pipeline, evaporator and voltage stabilizer of the nuclear power plant can all be replaced, the replacement cycle of the main equipment is long, and the construction is difficult and expensive

In addition, the reactor pressure vessel is a non-replaceable equipment during the operation of the main equipment of the nuclear power plant. If there is a defect in the safety end of the pressure vessel, it will directly lead to the early decommissioning of the power plant or spend a lot of resources on evaluation and calculation, which will seriously affect the safe and stable operation of the power plant.

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